Electric actuator for a scissor lift

ABSTRACT

An electric linear actuator for a lift assembly of a scissor lift includes a housing having a first end defining an aperture and a second end opposite the first end, an extending member received within the aperture and slidably coupled to the housing, a screw coupled to the housing, and an electric motor coupled to the housing and configured to drive rotation of the screw to control movement of the extending member along an axis of extension. The housing includes a mount configured to pivotally couple the housing to the lift assembly of the scissor lift. The mount is offset from the second end of the housing along the axis of extension such that the mount is positioned between the first end and the second end of the housing.

CROSS-REFERENCE TO RELATED APPLICATIONS

This application is a continuation of U.S. patent application Ser. No.17/863,863, filed Jul. 13, 2022, which is a continuation of U.S. patentapplication Ser. No. 16/811,851, filed Mar. 6, 2020, which claims thebenefit of U.S. Provisional Application No. 62/830,164, filed Apr. 5,2019, each of which is incorporated herein by reference in theirentirety.

BACKGROUND

Lift devices commonly include a vertically movable platform that issupported by a foldable series of linked supports. The linked supportsare arranged in an “X” pattern, crisscrossing with one another. Ahydraulic cylinder generally controls vertical movement of the platformby engaging and rotating (i.e., unfolding) the lowermost set of linkedsupports, which in turn unfolds the remainder of the series of linkedsupports within the system. The platform raises and lowers based uponthe degree of actuation by the hydraulic cylinder. A hydraulic cylindermay also control various other vehicle actions, such as, for example,steering or platform tilt functions. Lift devices using one or morehydraulic cylinders require an on-board reservoir tank to storehydraulic fluid for the lifting process.

SUMMARY

One exemplary embodiment relates to a lift device. The lift devicecomprises a base, a retractable lift mechanism, a work platform, alinear actuator, and an electromagnetic brake. The base has a pluralityof wheels. The retractable lift mechanism has a first end coupled to thebase and is moveable between an extended position and a retractedposition. The work platform is configured to support a load. The workplatform is coupled to and supported by a second end of the retractablelift mechanism. The linear actuator is configured to selectively movethe retractable lift mechanism between the extended position and theretracted position. The linear actuator has an electric motor. Theelectromagnetic brake is coupled to the linear actuator and movablebetween an engaged position, in which the retractable lift mechanism isprevented from moving between the extended position and the retractedposition, and a disengaged position, in which the retractable liftmechanism is allowed to move between the extended position and theretracted position. In the event of a power failure, the electromagneticbrake is biased toward the engaged position.

Another exemplary embodiment relates to a lift device. The lift devicecomprises a base, a retractable lift mechanism, a work platform, alinear actuator, and a descent control mechanism. The base has aplurality of wheels. The retractable lift mechanism has a first endcoupled to the base and is moveable between an extended position and aretracted position. The work platform is configured to support a load.The work platform is coupled to and supported by a second end of theretractable lift mechanism. The linear actuator is configured toselectively move the retractable lift mechanism between the extendedposition and the retracted position. The linear actuator has an electricmotor. The descent control mechanism is configured to reduce a speed atwhich the retractable lift mechanism is moved from the extended positionto the retracted position.

Another exemplary embodiment relates to a lift device. The lift devicecomprises a base, a retractable lift mechanism, a work platform, alinear actuator, an electromagnetic brake, a manual release device, anda descent control mechanism. The base has a plurality of wheels. Theretractable lift mechanism has a first end coupled to the base and ismoveable between an extended position and a retracted position. The workplatform is configured to support a load. The work platform is coupledto and supported by a second end of the retractable lift mechanism. Thelinear actuator is configured to selectively move the retractable liftmechanism between the extended position and the retracted position. Thelinear actuator has an electric motor. The electromagnetic brake iscoupled to the linear actuator and movable between an engaged position,in which the retractable lift mechanism is prevented from moving betweenthe extended position and the retracted position, and a disengagedposition, in which the retractable lift mechanism is allowed to movebetween the extended position and the retracted position, theelectromagnetic brake being biased toward the engaged position in theevent of a power failure. The manual release device is configured tomanually move the electromagnetic brake from the engaged position to thedisengaged position. The descent control mechanism is configured toreduce a speed at which the retractable lift mechanism is moved from theextended position to the retracted position.

Another exemplary embodiment relates to a lift vehicle. The lift vehicleincludes a base having a plurality of wheels, a battery arranged withinthe base, a drive motor powered by the battery and configured to driveat least one of the plurality of wheels and propel the base, aretractable lift including a first end coupled to the base and beingmovable between an extended position and a retracted position, a workplatform supported by a second end of the retractable lift, and a linearactuator having a lift motor with a rotor. The lift motor is powered bythe battery, and the linear actuator is coupled to the retractable liftso that rotation of the rotor moves the retractable lift between theextended position and the retracted position. The lift vehicle furtherincludes an electromagnetic brake coupled to a first side of the liftmotor. The electromagnetic brake includes a friction disk rotationallyfixed to the rotor for rotation therewith, an armature, and a wire coilconfigured to selectively receive power from the battery and, inresponse, produce an electromagnetic force on the armature to displacethe armature out of engagement with the friction disk, and in the eventof a power failure, the wire coil is de-energized and the armature isconfigured to be biased into engagement with the friction disk toprevent rotation of the rotor and, thereby, prevent the retractable liftfrom moving between the extended position and the retracted position.

Another exemplary embodiment relates to a lift vehicle. The lift vehicleincludes a base having a plurality of wheels, a battery arranged withinthe base, a drive motor powered by the battery and configured to driveat least one of the plurality of wheels and propel the base, aretractable lift including a first end coupled to the base and beingmovable between an extended position and a retracted position, a workplatform supported by a second end of the retractable lift, and a linearactuator including a lift motor powered by the battery. The linearactuator is coupled to the retractable lift so that rotation of the liftmotor moves the retractable lift between the extended position and theretracted position. The lift vehicle further includes an electromagneticbrake coupled to a first side of the lift motor. The electromagneticbrake is movable between an engaged position where the retractable liftis prevented from moving between the extended position and the retractedposition and a disengaged position where the retractable lift is allowedto move between the retracted positon and the disengaged position. Thelift vehicle further includes a centrifugal brake coupled to a secondside of the lift motor opposite to the first side. The centrifugal brakeis configured to limit a descent speed of the retractable lift.

Another exemplary embodiment relates to a lift vehicle. The life vehicleincludes a base having a plurality of wheels, a battery arranged withinthe base, a drive motor powered by the battery and configured to driveat least one of the plurality of wheels and propel the base, aretractable lift including a first end coupled to the base and beingmovable between an extended position and a retracted position, a workplatform supported by a second end of the retractable lift, and a linearactuator including a lift motor with a rotor, the lift motor beingpowered by the battery, The linear actuator is coupled to theretractable lift so that rotation of the rotor moves the retractablelift between the extended position and the retracted position. The liftvehicle further includes an electromagnetic brake coupled to a firstside of the lift motor. The electromagnetic brake includes a frictiondisk rotationally fixed to the rotor for rotation therewith, an armaturemovable between a disengaged position where the armature is separatedfrom the friction disk and an engaged position where the armature is inengagement with the friction disk, and a wire coil configured toselectively receive power from the battery and, in response, produce anelectromagnetic force on the armature to move the armature to thedisengaged position, and in the event of a power failure, the armatureis configured to be biased into the engaged position and, thereby,prevent the retractable lift from moving between the extended positionand the retracted position. The lift vehicle further includes a manualrelease coupled to a release tab and a centrifugal brake coupled to asecond side of the lift motor opposite to the first side. The releasetab is coupled to the armature so that actuation of the manual releasemoves the armature out of engagement with the friction disk. Thecentrifugal brake is configured to limit a descent speed of theretractable lift.

The invention is capable of other embodiments and of being carried outin various ways. Alternative exemplary embodiments relate to otherfeatures and combinations of features as may be recited herein.

BRIEF DESCRIPTION OF THE FIGURES

The disclosure will become more fully understood from the followingdetailed description, taken in conjunction with the accompanyingfigures, wherein like reference numerals refer to like elements, inwhich:

FIG. 1A is a side perspective view of a lift device in the form of ascissor lift, according to an exemplary embodiment;

FIG. 1B is another side perspective view of the lift device of FIG. 1A;

FIG. 2A is a side view of the lift device of FIG. 1A, shown in aretracted or stowed position;

FIG. 2B is a side perspective view of the lift device of FIG. 1A, shownin an extended or work position;

FIG. 3 is a side view of the lift device of FIG. 1A, depicting variousvehicle controllers;

FIG. 4 is a side view of a linear actuator of the lift device of FIG.1A;

FIG. 5 is a bottom view of the linear actuator of FIG. 4 ;

FIG. 6 is a side view of a push tube and a nut assembly of the linearactuator of FIG. 4 ;

FIG. 7A is a cross-sectional view of an electromagnetic brake of thelinear actuator of FIG. 4 , shown in an engaged position;

FIG. 7B is a cross-sectional view of the electromagnetic brake of FIG.7A, shown in a disengaged position;

FIG. 8 is a perspective view of a manual pull handle of a manual pulldevice of the lift device of FIG. 1A;

FIG. 9 is a side perspective view of the lift device of FIG. 1A, showingthe manual pull device;

FIG. 10 is a cross-sectional view of the electromagnetic brake of FIG.7A, shown including a release tab;

FIG. 11 is a perspective view of the linear actuator of FIG. 4 , showinga centrifugal brake;

FIG. 12 is a perspective view of the centrifugal brake of FIG. 11 ,showing the internal components of the centrifugal brake; and

FIG. 13 is a side perspective view of another lift device in the form ofa boom lift, according to another exemplary embodiment.

DETAILED DESCRIPTION

Before turning to the figures, which illustrate the exemplaryembodiments in detail, it should be understood that the presentapplication is not limited to the details or methodology set forth inthe description or illustrated in the figures. It should also beunderstood that the terminology is for the purpose of description onlyand should not be regarded as limiting.

Referring to the figures generally, the various exemplary embodimentsdisclosed herein relate to systems, apparatuses, and methods for thecontrolled descent of a work platform on a lift device. The lift deviceincludes an electromagnetic brake that is configured to engage in theevent of a power failure (e.g., a battery discharge or a control systemfailure) to hold the work platform in place (i.e., at a constantheight). The lift device further includes a manual release mechanism toselectively release the electromagnetic brake to lower the work platformin the event of a battery discharge or a control system failure. Thelift device further includes a descent limiting mechanism that limitsthe speed at which the work platform is allowed to lower when theelectromagnetic brake is disengaged. Thus, the lift device allows forthe work platform and any worker on the work platform to be safelylowered from a deployed work position in the event of a batterydischarge or a control system failure.

According to the exemplary embodiment depicted in FIGS. 1A and 1B, avehicle, shown as vehicle 10, is illustrated. The vehicle 10 may be ascissor lift, for example, which can be used to perform a variety ofdifferent tasks at various elevations. The vehicle 10 includes a base 12supported by wheels 14A, 14B positioned about the base 12. The vehicle10 further includes a battery 16 positioned on board the base 12 of thevehicle 10 to supply electrical power to various operating systemspresent on the vehicle 10.

The battery 16 can be a rechargeable lithium-ion battery, for example,which is capable of supplying a direct current (DC) or alternatingcurrent (AC) to controls, motors, actuators, and the like included onboard the vehicle 10. The battery 16 can include at least one input 18capable of receiving electrical current to recharge the battery 16. Insome embodiments, the input 18 is a port capable of receiving a plug inelectrical communication with an external power source, like a walloutlet. The battery 16 can be configured to receive and store electricalcurrent from one of a traditional 120 V outlet, a 240 V outlet, a 480 Voutlet, an electrical power generator, or another suitable electricalpower source.

The vehicle 10 further includes a retractable lift mechanism, shown as ascissor lift mechanism 20, coupled to the base 12. The scissor liftmechanism 20 supports a work platform 22 (shown in FIG. 3 ). Asdepicted, a first end 23 of the scissor lift mechanism 20 is anchored tothe base 12, while a second end 24 of the scissor lift mechanism 20supports the work platform 22. As illustrated, the scissor liftmechanism 20 is formed of a foldable series of linked support members25. The scissor lift mechanism 20 is selectively movable between aretracted or stowed position (shown in FIG. 2A) and an extended,deployed, or work position (shown in FIG. 2B) using an actuator, shownas linear actuator 26. The linear actuator 26 is an electric actuator.The linear actuator 26 controls the orientation of the scissor liftmechanism 20 by selectively applying force to the scissor lift mechanism20. When a sufficient force is applied to the scissor lift mechanism 20by the linear actuator 26, the scissor lift mechanism 20 unfolds orotherwise deploys from the stowed or retracted position into the workposition. Because the work platform 22 is coupled to the scissor liftmechanism 20, the work platform 22 is also raised away from the base 12in response to the deployment of the scissor lift mechanism 20.

As shown in FIG. 3 , the vehicle 10 further includes a vehiclecontroller 27 and a lift motor controller 28. The vehicle controller 27is in communication with the lift motor controller 28 and is configuredto control various driving systems on the vehicle 10. The lift motorcontroller 28 is in communication with the linear actuator 26 and isconfigured to control the movement of the scissor lift mechanism 20.Communication between the lift motor controller 28 and the linearactuator 26 and/or between the vehicle controller 27 and the lift motorcontroller 28 can be provided through a hardwired connection or througha wireless connection (e.g., Bluetooth, Internet, cloud-basedcommunication system, etc.). It should be understood that each of thevehicle controller 27 and the lift controller 28 includes variousprocessing and memory components configured to perform the variousactivities and methods described herein. For example, in some instances,each of the vehicle controller 27 and the lift controller 28 includes aprocessing circuit having a processor and a memory. The memory isconfigured to store various instructions configured to, when executed bythe processor, cause the vehicle 10 to perform the various activitiesand methods described herein.

As illustrated in the exemplary embodiment provided in FIGS. 4-6 , thelinear actuator 26 includes a push tube assembly 30, a gear box 32, andan electric lift motor 34. The push tube assembly 30 includes aprotective outer tube 36 (shown in FIGS. 4 and 5 ), a push tube 38, anda nut assembly 40 (shown in FIG. 6 ). The protective outer tube 36 has atrunnion connection portion 42 disposed at a proximal end 44 thereof.The trunnion connection portion 42 is rigidly coupled to the gear box32, thereby rigidly coupling the protective outer tube 36 to the gearbox 32. The trunnion connection portion 42 further includes a trunnionmount 45 that is configured to rotatably couple the protective outertube 36 to one of the support members 25 (as shown in FIG. 2B).

The protective outer tube 36 further includes an opening at a distal end46 thereof. The opening of the protective outer tube 36 is configured toslidably receive the push tube 38. The push tube 38 includes aconnection end, shown as trunnion mount 48, configured to rotatablycouple the push tube 38 to another one of the support members 25 (asshown in FIG. 2B). As will be discussed below, the push tube 38 isslidably movable and selectively actuatable between an extended position(shown in FIG. 2B) and a retracted position (shown in FIG. 4 ).

Referring now to FIG. 6 , the push tube 38 is rigidly coupled to the nutassembly 40, such that motion of the nut assembly 40 results in motionof the push tube 38. The push tube 38 and the nut assembly 40 envelop acentral screw rod. The central screw rod is rotatably engaged with thegear box 32 and is configured to rotate within the push tube 38 and thenut assembly 40, about a central axis of the push tube assembly 30. Thenut assembly 40 is configured to engage the central screw rod andtranslate the rotational motion of the central screw rod intotranslational motion of the push tube 38 and the nut assembly 40, withrespect to the central screw rod, along the central axis of the pushtube assembly 30. In some embodiments, the nut assembly 40 may be, forexample, a ball screw assembly or a roller screw assembly. In some otherembodiments, the nut assembly 40 may be any other suitable assembly fortranslating rotational motion of the central screw rod intotranslational motion of the push tube 38 and the nut assembly 40.

Referring again to FIG. 4 , the lift motor 34 is configured toselectively provide rotational actuation to the gear box 32. Therotational actuation from the lift motor 34 is then translated throughthe gear box 32 to selectively rotate the central screw rod of the pushtube assembly 30. The rotation of the central screw rod is thentranslated by the nut assembly 40 to selectively translate the push tube38 and the nut assembly 40 along the central axis of the push tubeassembly 30. Accordingly, the lift motor 34 is configured to selectivelyactuate the push tube 38 between the extended position and the retractedposition. Thus, with the trunnion mount 45 of the protective outer tube36 and the trunnion mount 48 of the push tube 38 each rotatably coupledto their respective support members 25, the lift motor 34 is configuredto selectively move the scissor lift mechanism 20 to various heightsbetween and including the retracted or stowed position and the deployedor work position.

The lift motor 34 may be an AC motor (e.g., synchronous, asynchronous,etc.) or a DC motor (shunt, permanent magnet, series, etc.). In someinstances, the lift motor 34 is in communication with and powered by thebattery 16. In some other instances, the lift motor 34 may receiveelectrical power from another electricity source on board the vehicle10.

As depicted in the exemplary embodiment shown in FIGS. 7A and 7B, thelift motor 34 includes an electromagnetic brake 50 configured to holdthe work platform 22 in place (i.e., at a constant height) in the caseof a battery discharge or a control system failure. As illustrated inFIGS. 7A and 7B, the electromagnetic brake 50 includes a pressure plate52, a friction disk 54, an armature 56, a magnetic body 58, and a wirecoil 60. As illustrated, the pressure plate 52 is disposed at a firstend 62 of the electromagnetic brake 50. The pressure plate 52 surroundsa hub 64. The hub 64 is fixed to a rotor 66 of the lift motor 34, suchthat the hub 64 and the rotor 66 are rotationally coupled (e.g.,rotation of one of the hub 64 and the rotor 66 results in the rotationof the other of the hub 64 and the rotor 66). The friction disk 54 isdisposed adjacent the pressure plate 52. The friction disk 54 is fixedto the hub 64, such that of the hub 64, the rotor 66, and the frictiondisk 54 are all rotationally coupled (e.g., rotation of one of the hub64, the rotor 66, and the friction disk 54 results in the rotation ofthe other two of the hub 64, the rotor 66, and the friction disk 54).The armature 56 is disposed adjacent the friction disk 54, and is biasedinto contact with the friction disk 54 by engagement springs 68.

The magnetic body 58 and the wire coil 60 are disposed at a second end70 of the electromagnetic brake 50. The magnetic body 58 and the wirecoil 60 are configured to selectively produce a magnetic force on thearmature 56 to pull the armature 56 toward the magnetic body 58.

Referring now to FIG. 7A, the electromagnetic brake 50 is shown in anengaged position. Specifically, when there is no power applied to thewire coil 60 of the lift motor 34, the magnetic body 58 and the wirecoil 60 do not produce any magnetic force on the armature 56. As such,the engagement springs 68 bias the armature 56 against the friction disk54, thereby preventing rotation of the friction disk 54. Because thefriction disk 54 is fixed to the hub 64, and the hub is rigidly coupledto the rotor 66, the rotor 66 is also prevented from rotating, therebypreventing the work platform 22 from moving vertically (e.g., becausethe central screw rod is prevented from spinning, such that the linearactuator is prevented from translating). Accordingly, when no power isapplied to the wire coil 60 of the lift motor 34, the electromagneticbrake 50 is biased toward the engaged position.

Referring now to FIG. 7B, the electromagnetic brake 50 is shown in adisengaged position. Specifically, when power (e.g., a current) isapplied to the wire coil 60 of the lift motor 34, the magnetic body 58and the wire coil 60 produce an electromagnetic force on the armature56, compressing the engagement springs 68 and pulling the armature 56out of contact with the friction disk 54. Accordingly, the friction disk54, the hub 64, and the rotor 66 are all free to rotate. As such, thelift motor 34 is allowed to function normally.

During normal operation, when the lift motor 34 is commanded to lift orlower the work platform 22, power is also applied to the wire coil 60 toallow for the lift motor 34 to function as intended. Then, when the liftmotor 34 is not being commanded to lift or lower the work platform 22,power is not applied to the wire coil 60, such that the friction disk 54is engaged by the armature 56, and the work platform 22 is preventedfrom moving vertically.

As such, in the event of a power failure (e.g., the battery 16 isdischarged or the control system fails), when power is cut from the wirecoil 60, the electromagnetic brake 50 is configured to automaticallyreturn to the engaged position, and the scissor lift mechanism 20 isprevented from moving between the extended position and the retractedposition. In some embodiments, if the battery 16 is discharged or thecontrol system fails when the scissor lift mechanism 20 is in theextended position (i.e., the work platform 22 is in a raised position)it may be desired to allow for the work platform 22 (and any usersworking on the work platform 22) to be safely lowered from the raised ordeployed position back down to the stowed or lowered position.

Accordingly, as illustrated in the exemplary embodiment shown in FIGS.8-12 , the vehicle 10 further includes a manual release device 72 and adescent limiting mechanism, shown as centrifugal brake 74. The manualrelease device 72 is configured to manually move the electromagneticbrake 50 into the disengaged position, such that the work platform 22can be lowered due to gravity. The centrifugal brake 74 is configured toprovide resistance to and modulate (e.g., mechanically reduce) the speedat which the work platform 22 is lowered.

Specifically, the manual release device 72 includes a manual pull handle76 (shown in FIGS. 8 and 9 ) that is connected to a release tab 78(shown in FIG. 10 ) through a Bowden cable 80 (shown in FIG. 9 ). As themanual pull handle 76 is pulled, the Bowden cable 80 pulls on therelease tab 78, which is fixed to the armature 56. Accordingly, thearmature 56 is moved out of contact with the friction disk 54, therebymanually moving the electromagnetic brake 50 into the disengagedposition and allowing the work platform 22 to lower.

The centrifugal brake 74 is configured to modulate (e.g., mechanicallyreduce) the speed at which the rotor 66 is allowed to rotate.Specifically, the centrifugal brake 74 prevents the work platform 22from descending too rapidly when the electromagnetic brake 50 isdisengaged. Specifically, as best shown in FIG. 12 , the centrifugalbrake 74 includes a rotor connection portion 82, a pair of weights 84, apair of retention springs 86, and a casing 88. The rotor connectionportion 82 is rotationally fixed to the rotor 66 (e.g., through a keywayconnection, a set screw, or any other suitable connection). The pair ofweights 84 are disposed on opposite sides of the rotor connectionportion 82. The pair of weights 84 are configured to engage the rotorconnection portion 82, such that rotation of the rotor connectionportion 82 results in rotation of the pair of weights 84, and viceversa. Each weight 84 of the pair of weights 84 includes a frictionalouter surface 90. The pair of retention springs 86 are configured tomaintain an inwardly-biased force on the pair of weights 84, generallydirected toward the rotor 66.

During operation, as the rotor 66 rotates, the pair of weights 84 tendto move radially outward, away from the rotor 66. The pair of retentionsprings 86 are configured to provide a radially-inward (i.e., toward therotor 66) force onto the weights 84, preventing the frictional outersurface 90 of the weights 84 from contacting a frictional inner surface92 of the casing 88, and thus from reducing the rotational speed of therotor 66, until the rotor 66 exceeds a predetermined rotational speed.That is, in some embodiments, the centrifugal brake 74 is configured toreduce the rotational speed of the rotor 66 once the rotational speed ofthe rotor 66 reaches or exceeds the predetermined rotational speed.

In some embodiments, the predetermined rotational speed may beapproximately 2050 rpm. In some other embodiments, the predeterminedrotational speed may be between 1850 rpm and 2250 rpm. In yet some otherembodiments, the predetermined rotational speed may be more than 2250rpm or less than 1850 rpm, as desired for a given application. Once therotor 66 exceeds the predetermined rotational speed, the requiredcentripetal force needed to retain the weights adjacent the rotorconnection portion 82 exceeds the spring force, allowing the weights tomove radially outward. As such, the frictional outer surface 90 of theweights 84 contacts the frictional inner surface 92 of the casing 88,which effectively limits the rotational speed of the rotor 66.

As such, during operation, in the event that the battery 16 isdischarged or the control system fails, the manual release device 72 andthe centrifugal brake 74 allow for the work platform 22 to be safelylowered from the deployed position. Further, in the event that themanual pull handle 76 is pulled during normal operation, the lift motorcontroller 28 may be configured to control the descent of the workplatform 22 using the lift motor 34.

Although the illustrated centrifugal brake 74 is shown opposite the gearbox 32 from the lift motor 34, in some embodiments, the centrifugalbrake 74 may alternatively be located between the gear box 32 and thelift motor 34. In some other embodiments, the centrifugal brake 74 maybe alternatively located opposite the electromagnetic brake 50 from thelift motor 34.

Further, in some embodiments, the descent limiting mechanism may bereplaced by various other types of brake mechanisms that are configuredto limit the rotational speed of the rotor 66. For example, in someembodiments, the linear actuator 26 may alternatively or additionallyinclude a shoe brake, a drum brake, a disk brake, or any other suitablebrake mechanism, as desired for a given application.

Additionally, in some embodiments, in addition to or in place of thecentrifugal brake 74, the linear actuator 26 may include a descentlimiting mechanism in the form of a permanent magnet motor. Thepermanent magnet motor has terminals that are biased toward a shuntedposition, but are actively held open during normal operation. As such,in the event of the battery 16 being discharged or the control systemfailing, the terminals are shunted together, such that the permanentmagnet motor acts like a generator. With the permanent magnet motoracting like a generator, the speed at which the rotor 66 is allowed torotate would be effectively reduced.

In some embodiments, the lift motor 34 may be a permanent magnet motor,and may be configured to both selectively actuate the linear actuator26, while also having terminals that are biased toward a shuntedposition in the case of the battery 16 being discharged or the controlsystem failing, such that the lift motor 34 acts as a generator andreduces the speed of the rotor 66 in the case of a battery discharge ora control system failure.

Referring again to FIGS. 1A and 1B, the battery 16 can also be incommunication with the vehicle controller 27, which can command thebattery 16 to selectively supply electrical power to a drive motor 94 topropel the vehicle 10. The drive motor 94 may similarly be an AC motor(e.g., synchronous, asynchronous, etc.) or a DC motor (shunt, permanentmagnet, series, etc.) for example, which receives electrical power fromthe battery 16 or other electricity source on board the vehicle 10 andconverts the electrical power into rotational energy in a drive shaft.The drive shaft can be used to drive the wheels 14A, 14B of the vehicle10 using a transmission. The transmission can receive torque from thedrive shaft and subsequently transmit the received torque to a rear axle96 of the vehicle 10. Rotating the rear axle 96 also rotates the rearwheels 14A on the vehicle 10, which propels the vehicle 10.

The rear wheels 14A of the vehicle 10 can be used to drive the vehicle,while the front wheels 14B can be used to steer the vehicle 10. In someembodiments, the rear wheels 14A are rigidly coupled to the rear axle96, and are held in a constant orientation relative to the base 12 ofthe vehicle 10 (e.g., approximately aligned with an outer perimeter 98of the vehicle 10). In contrast, the front wheels 14B are pivotallycoupled to the base 12 of the vehicle 10. The wheels 14B can be rotatedrelative to the base 12 to adjust a direction of travel for the vehicle10. Specifically, the front wheels 14B can be oriented using anelectrical steering system 100. In some embodiments, the steering system100 may be completely electrical in nature, and may not include any formof hydraulics.

It should be appreciated that, while the retractable lift mechanismincluded on vehicle 10 is a scissor lift mechanism, in some instances, avehicle may be provided that alternatively includes a retractable liftmechanism in the form of a boom lift mechanism. For example, in theexemplary embodiment depicted in FIG. 13 , a vehicle, shown as vehicle210, is illustrated. The vehicle 210 includes a retractable liftmechanism, shown as boom lift mechanism 220. The boom lift mechanism 220is similarly formed of a foldable series of linked support members 225.The boom lift mechanism 220 is selectively movable between a retractedor stowed position and a deployed or work position using a plurality ofactuators 226. Each of the plurality of actuators 226 is a linearactuator similar to the linear actuator 26.

It should be further appreciated that the linear actuators used in thelift mechanism 20, 220, as well as in the steering system 100, may beincorporated into nearly any type of electric vehicle. For example, theelectric systems described herein can be incorporated into, for example,a scissor lift, an articulated boom, a telescopic boom, or any othertype of aerial work platform.

Advantageously, vehicles 10, 210 may be fully-electric lift devices. Allof the electric actuators and electric motors of vehicles 10, 210 can beconfigured to perform their respective operations without requiring anyhydraulic systems, hydraulic reservoir tanks, hydraulic fluids, enginesystems, etc. That is, both vehicles 10, 210 may be completely devoid ofany hydraulic systems and/or hydraulic fluids generally. Saiddifferently, both vehicles 10, 210 may be devoid of any moving fluids.Traditional lift device vehicles do not use a fully-electric system andrequire regular maintenance to ensure that the various hydraulic systemsare operating properly. As such, the vehicles 10, 210 may use electricmotors and electric actuators, which allows for the absence ofcombustible fuels (e.g., gasoline, diesel) and/or hydraulic fluids. Assuch, the vehicles 10, 210 may be powered by batteries, such as battery16, that can be re-charged when necessary.

Although this description may discuss a specific order of method steps,the order of the steps may differ from what is outlined. Also two ormore steps may be performed concurrently or with partial concurrence.Such variation will depend on the software and hardware systems chosenand on designer choice. All such variations are within the scope of thedisclosure. Likewise, software implementations could be accomplishedwith standard programming techniques with rule-based logic and otherlogic to accomplish the various connection steps, processing steps,comparison steps, and decision steps.

As utilized herein, the terms “approximately”, “about”, “substantially”,and similar terms are intended to have a broad meaning in harmony withthe common and accepted usage by those of ordinary skill in the art towhich the subject matter of this disclosure pertains. It should beunderstood by those of skill in the art who review this disclosure thatthese terms are intended to allow a description of certain featuresdescribed and claimed without restricting the scope of these features tothe precise numerical ranges provided. Accordingly, these terms shouldbe interpreted as indicating that insubstantial or inconsequentialmodifications or alterations of the subject matter described and claimedare considered to be within the scope of the invention as recited in theappended claims.

It should be noted that the term “exemplary” as used herein to describevarious embodiments is intended to indicate that such embodiments arepossible examples, representations, and/or illustrations of possibleembodiments (and such term is not intended to connote that suchembodiments are necessarily extraordinary or superlative examples).

The terms “coupled,” “connected,” and the like, as used herein, mean thejoining of two members directly or indirectly to one another. Suchjoining may be stationary (e.g., permanent, etc.) or moveable (e.g.,removable, releasable, etc.). Such joining may be achieved with the twomembers or the two members and any additional intermediate members beingintegrally formed as a single unitary body with one another or with thetwo members or the two members and any additional intermediate membersbeing attached to one another.

References herein to the positions of elements (e.g., “top,” “bottom,”“above,” “below,” “between,” etc.) are merely used to describe theorientation of various elements in the figures. It should be noted thatthe orientation of various elements may differ according to otherexemplary embodiments, and that such variations are intended to beencompassed by the present disclosure.

The hardware and data processing components used to implement thevarious processes, operations, illustrative logics, logical blocks,modules and circuits described in connection with the embodimentsdisclosed herein may be implemented or performed with a general purposesingle- or multi-chip processor, a digital signal processor (DSP), anapplication specific integrated circuit (ASIC), a field programmablegate array (FPGA), or other programmable logic device, discrete gate ortransistor logic, discrete hardware components, or any combinationthereof designed to perform the functions described herein. A generalpurpose processor may be a microprocessor, or, any conventionalprocessor, or state machine. A processor also may be implemented as acombination of computing devices, such as a combination of a DSP and amicroprocessor, a plurality of microprocessors, one or moremicroprocessors in conjunction with a DSP core, or any other suchconfiguration. The memory (e.g., memory, memory unit, storage device)may include one or more devices (e.g., RAM, ROM, Flash memory, hard diskstorage) for storing data and/or computer code for completing orfacilitating the various processes, layers and modules described in thepresent disclosure. The memory may be or include volatile memory ornon-volatile memory, and may include database components, object codecomponents, script components, or any other type of informationstructure for supporting the various activities and informationstructures described in the present disclosure. According to anexemplary embodiment, the memory is coupled to the processor to form aprocessing circuit and includes computer code for executing (e.g., bythe processor) the one or more processes described herein.

It is important to note that the construction and arrangement of theelectromechanical variable transmission as shown in the exemplaryembodiments is illustrative only. Although only a few embodiments of thepresent disclosure have been described in detail, those skilled in theart who review this disclosure will readily appreciate that manymodifications are possible (e.g., variations in sizes, dimensions,structures, shapes and proportions of the various elements, values ofparameters, mounting arrangements, use of materials, colors,orientations, etc.) without materially departing from the novelteachings and advantages of the subject matter recited. For example,elements shown as integrally formed may be constructed of multiple partsor elements. It should be noted that the elements and/or assemblies ofthe components described herein may be constructed from any of a widevariety of materials that provide sufficient strength or durability, inany of a wide variety of colors, textures, and combinations.Accordingly, all such modifications are intended to be included withinthe scope of the present inventions. Other substitutions, modifications,changes, and omissions may be made in the design, operating conditions,and arrangement of the preferred and other exemplary embodiments withoutdeparting from scope of the present disclosure or from the spirit of theappended claims.

What is claimed is:
 1. An electric linear actuator for a lift assemblyof a scissor lift, the electric linear actuator comprising: a housinghaving a first end defining an aperture and a second end opposite thefirst end, the housing including a mount configured to pivotally couplethe housing to the lift assembly of the scissor lift; an extendingmember received within the aperture and slidably coupled to the housing;a screw coupled to the housing; and an electric motor coupled to thehousing and configured to drive rotation of the screw to controlmovement of the extending member along an axis of extension, wherein themount is offset from the second end of the housing along the axis ofextension such that the mount is positioned between the first end andthe second end of the housing.
 2. The electric linear actuator of claim1, wherein the housing includes an elongated member defining theaperture and a gearbox coupling the electric motor to the screw, andwherein the mount is positioned between the gearbox and the elongatedmember.
 3. The electric linear actuator of claim 2, wherein the electricmotor is offset from the axis of extension.
 4. The electric linearactuator of claim 3, wherein the electric motor and the elongated memberboth extend away from the gearbox in a first direction.
 5. The electriclinear actuator of claim 4, further comprising a brake configured toselectively limit movement of the extending member relative to thehousing, wherein the electric motor is positioned between the gearboxand the brake.
 6. The electric linear actuator of claim 5, furthercomprising: a handle; a cable coupled to the handle and the brake andconfigured to transfer a force applied by a user on the handle to thebrake to control engagement of the brake; and a bracket coupling thecable to the electric motor.
 7. The electric linear actuator of claim 1,wherein the housing includes an elongated member defining the aperture,wherein the elongated member and the extending member are substantiallycentered about the axis of extension, and wherein the mount includes aprotrusion that extends substantially perpendicular to the axis ofextension.
 8. The electric linear actuator of claim 7, wherein theprotrusion is a pin.
 9. The electric linear actuator of claim 7, whereinthe protrusion is a first protrusion, and wherein the mount furtherincludes a second protrusion extending substantially perpendicular tothe axis of extension.
 10. The electric linear actuator of claim 9,wherein the first protrusion extends away from the elongated member in afirst direction, and wherein the second protrusion extends away from theelongated member in a second direction opposite the first direction. 11.The electric linear actuator of claim 10, wherein the mount is a firstmount, and wherein the extending member includes a second mountconfigured to pivotally couple the housing to the lift assembly of thescissor lift, wherein the second mount defines a mount aperture thatextends substantially perpendicular to the axis of extension.
 12. Theelectric linear actuator of claim 11, wherein the mount aperture extendslaterally through the first mount from a first side of the first mountto an opposing second side of the first mount.
 13. The scissor lift ofclaim 1, wherein the housing includes an outer tube defining theaperture, and wherein the extending member is push tube that receivesthe screw such that the push tube extends between the screw and theouter tube in at least one position of the push tube.
 14. The scissorlift of claim 13, further comprising a nut coupled to the push tube andengaging the screw.
 15. An electric linear actuator for a lift device,the electric linear actuator comprising: a housing including anelongated portion defining an aperture and a second portion extendingsubstantially perpendicular to the elongated portion; an extendingmember received within the aperture and slidably coupled to the housing;a screw received within the elongated portion of the housing; anelectric motor coupled to the second portion of the housing andconfigured to drive rotation of the screw to control extension of theelectric linear actuator; a brake configured to selectively preventmovement of the electric motor; a handle; and a cable coupling thehandle to the brake and configured to disengage the brake to permitmovement of the electric motor in response to a user interaction withthe handle.
 16. The electric linear actuator of claim 15, wherein thecable is configured to apply a force onto the brake to disengage thebrake in response to a user pulling the handle.
 17. The electric linearactuator of claim 16, wherein the cable includes a first end coupled tothe handle and a second end coupled to the brake, and wherein the handleincludes a receiving portion that receives the first end of the cableand an interface portion that extends substantially perpendicular to thereceiving portion.
 18. The electric linear actuator of claim 15, furthercomprising a bracket coupling the cable to the electric motor, whereinthe electric motor extends between the second portion of the housing andthe brake.
 19. The electric linear actuator of claim 15, wherein theelongated portion and the electric motor extend away from the secondportion of the housing in a first direction, and wherein the brake isoffset from the second portion of the housing in the first direction.20. An electric linear actuator for a lift assembly of a scissor lift,the electric linear actuator comprising: a housing having a first enddefining an aperture and a second end opposite the first end, thehousing including: an elongated member defining the aperture; a gearboxextending substantially perpendicular to the elongated member; and afirst mount positioned between the gearbox and the elongated member, thefirst mount including a pair of protrusions extending outward along afirst lateral axis; an extending member received within the aperture andmovable relative to the housing along a longitudinal axis, the extendingmember including a second mount defining a passage that extends along asecond lateral axis; a screw coupled to the housing; an electric motorcoupled to the gearbox and configured to drive rotation of the screw tocontrol movement of the extending member along the longitudinal axis,wherein the elongated member and the electric motor both extend awayfrom the gearbox in a first direction a brake coupled to the electricmotor such that the electric motor extends between the brake and thegearbox, wherein the brake is configured to selectively limit rotationof the screw; a cable coupled to a handle and the brake, wherein thecable is configured to impart a force on the brake in response to a userpulling the handle; and a bracket coupling the cable to the electricmotor.